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Implant Interactions with Orthodontics
original article
Implant Interactions with Orthodontics Frank Celenza, DDS
Abstract
Private practice; New York, NY 10021; Private practice, Englewood Cliffs, NJ 07632 Corresponding Author: Frank Celenza, DDS, 880 Fifth Avenue, New York, NY 10021; E-mail: [email protected]. J Evid Base Dent Pract 2012:S1: [192-201] 1532-3382/$36.00 © 2012 Elsevier Inc. All rights reserved.
Many situations arise in which orthodontic therapy in conjunction with implant modalities is beneficial, relevant or necessary. These situations might entail orthodontic treatment preparatory to the placement of an implant, such as in the site preparation for implant placement. Traditionally, this has been somewhat well understood, but there are certain guidelines that must be adhered to as well as diagnostic steps that must be followed. Provision of adequate space for implant placement is of paramount importance, but there is also the consideration of tissue manipulation and remodeling which orthodontic therapy can achieve very predictably and orthodontists should be well versed in harnessing and employing this modality of site preparation. In this way, hopeless teeth that are slated for extraction can still be utilized by orthodontic extraction to augment tissues, both hard and soft, thereby facilitating site development. On the corollary, and representing a significant shift in treatment sequencing, there are many situations in which orthodontic mechanotherapy can be simplified, expedited, and facilitated by the placement of an implant and utilization as an integral part of the mechanotherapy. Implants have proven to provide excellent anchorage, and have resulted in a new class of anchorage known as “absolute anchorage”. Implants can be harnessed as anchors both in a direct and indirect sense, depending upon the dictates of the case. Further, this has led to the development of orthodontic miniscrew systems and techniques, which can have added features such as flexibility in location and placement, as well as ease of use and removal. As orthodontic appliances evolve, the advent of aligner therapy has become mainstream and well accepted, and many of the aforementioned combined treatment modalities can and should be incorporated into this relatively new treatment modality as well.
Introduction
W
hereas the acceptance of implant therapy has deeply affected the surgical and restorative specialties, it has been this author’s observation that the specialty of orthodontics has not experienced this transformation in nearly as dramatic a fashion. Although orthodontists have clearly become aware of implant modalities and incorporated them into treatment plans, for the most part, the dayto-day practice of orthodontics has not changed greatly, certainly not to the extent that the other specialties have had to undergo transformation. For the most part, the orthodontist may be aware that a congenitally missing tooth, for example, will now be replaced by an implant-supported restoration instead of a multiunit bridge,
Keywords: Implant, orthodontics, anchorage, miniscrew, tad, invisalign, interdisciplinary site development
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periodontal ligament as a result of orthodontic stimuli. Additionally, the gingival and soft tissues also respond to tooth movement.
Figure 1. These radiographs depict the situation of 2 seemingly hopeless maxillary central incisors, on the left, and the use of orthodontic site development. The right side is after 4 months of orthodontic eruption and 4 months of stabilization, illustrating the alteration of what would have been a severe extraction socket into an incipient one, making for a much more favorable implant placement environment.
A recent study quantified the benefits of “Orthodontic Extraction” and found the efficacy of regenerating hard tissue to be 70% and that for gingival augmentation to be 60%.1 Further, the residual attachment level of a tooth was not considered to be a limitation. As eruption is a purely vertical movement, and occurs in such a way that the existing attachment around a tooth is placed under pure tension, it does not seem to be insulting to the periodontal attachment apparatus if there is pathology present. More specifically, it seems that when a root is erupted, even if there are cytotoxic regions on that root surface, because it is being moved away from its investing attachment, the periodontal ligament is not insulted and will continue to impart tension to its bony margins and result in deposition. This is often observed despite the presence of an inflammatory environment. What this means is that even in severely compromised teeth, which are destined for extraction, the positive physiologic benefits of orthodontic tissue alteration can still be harnessed to result in morphologic remodeling, or site development. Orthodontic extrusion of teeth with advanced periodontal disease can still have positive clinical and histologic results.2
and so may consequently pay more attention to tooth position and parallelism to facilitate this restoration, but that largely does not change the sequencing, execution, or timing of the treatment, in the orthodontist’s mind. Nonetheless, it is this author’s contention that the specialty of orthodontics is poised, when armed with an understanding of the power and flexibility of implants, to experience a transformation not unlike the aforementioned specialties encountered. When adopted as an integral component of an orthodontic appliance, implants offer the ability to dramatically alter conventional mechanotherapy. The implications range from increased predictability, to simplified mechanics, elimination of patient compliance, decreased treatment time, and perhaps most importantly, expanded treatment possibilities.
As a result of this body of knowledge, teeth that have historically been labeled as hopeless, and slated for extraction, can still be used for physiologic benefit, when appropriate, to impart orthodontic augmentation, or site development. Such teeth, although hopeless, are thereby not to be considered useless, as there is biologic benefit to be realized before their eventual extraction (Fig. 1). Last, and perhaps most importantly, the tissue that is formed by virtue of this orthodontic augmentation, has been shown to be vital tissue3 (Fig. 2). This is because this tissue is formed through the body’s reparative capacity, remodeling in response to orthodontic stimulus, and so it results from physiologic alteration. Unlike allografts and even transplanted tissues of autografts, this tissue is naturally formed in its location. This vital tissue has beneficial implications with respect to subsequent demands placed on it, such as osseointegration to a planned implant placement.
The purpose of this article was to delineate and illustrate some interactions between orthodontics and implants that may be commonly encountered. The topic is divided into 2 distinct phases: the first addressing interactions that orthodontics can effect on sites preparatory to the placement of implants, and the second addressing the effect that implants can have on orthodontics when placed before or during the orthodontic phase and used as part of mechanotherapy.
For Spatial Relations
Orthodontic Interactions Preparatory to Implant Placement
With the advent of implants for tooth replacement, it could be argued that the need for accurate tooth position is more important. Whereas previous tooth replacements might have been accomplished with fixed prostheses, for example, these types of restorations did not require absolute parallelism of roots. In the preparation of a crown or retainer, there is room for correction of less than ideal tooth position, and in the
For Tissue Management Orthodontic tooth movement imparts many alterations on the tissues and supporting structures. It has long been understood that the investing bone tissue remodels in response to pressure and tension that is imparted to it through the
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Figure 2. Here is a histologic image of the bone that was formed through orthodontic stimulus in the previous case. Of particular interest is the appearance of osteocytes within every lacuna, indicating the use of the bodies’ remodeling capacity to form vital bone.
Figure 3. Clinical (A) and radiographic (B) images of a post orthodontic result. Although the incisal edges are properly aligned and the clinical landmarks appear satisfactory for implant placement in the clinical photo, the radiographic picture clearly illustrates inadequate root alignment and space for implant placement.
A
B fabrication of a restoration, new crown contours and “prosthetic tooth positioning” can and routinely do occur. However, if a missing tooth is to be replaced by an implant, the need for accurate site preparation in terms of special relations becomes paramount. Planning for an implant requires a minimum intercoronal space, as was needed in the fixed restoration. More importantly, the implant modality also dictates that there is proper interradicular space to permit the surgical placement of the device and to ensure that root damage to the neighboring teeth is prevented. Consequently, parallelism of teeth, and roots, is essential, and accomplishing this requires that the orthodontic phase of implant site preparation be monitored at the radiographic level, not by clinical visualization. With the use of modern edgewise straightwire appliances, the process of bracket placement on the actual teeth is necessarily an important, if not the most important, step in the set up of a case. With time and experience, most practitioners become adept at direct bonding by sight, usually relying on dental anatomy and landmarks for reference.This method usually suffices for most situations, but the clinician is cautioned to be wary of deviations in crown contour, wear, and root angulations that are frequently encountered in semiedentulous cases. Only by carefully evaluating accurate radiographs will these deviations be appreciated. Further, goodquality periapical radiographs are preferable in this context, owing to their higher level of detail and more reliable orientation than a panorex. In any case, the practitioner is well advised to position bracket placements with consideration to radiographic landmarks, not clinical (Fig. 3).
Orthodontic Interactions After Implant Placement The orthodontist manages equal and opposite actions by controlling anchorage, which is defined as a body’s resistance to displacement. When the anchor units are natural teeth, as they traditionally have been, then they are equally susceptible to movement as are the active teeth. Various measures are taken to ensure that the desirable movements occur and the anchor segments are preserved, but anchor management remains at the very core of orthodontic challenges. Most frequently, in the natural dentition, anchor segments overpower active segments by outnumbering them. For
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Figure 4. A potential anchorage system in the natural dentition. An orthodontic fixed appliance is used as a splint to join all of the teeth from the lateral incisor posteriorly to effectively outnumber the single active central incisor tooth thereby enabling its controlled movement.
TABLE 1. This table compares the function dictates in 3 aspects between an occlusally loaded implant and an orthodontically loaded one. In all 3 regards, orthodontic load is significantly less taxing. Magnitude
Dental Implant
Ortho Implant
High (Kg)
Low (Oz)
Duration
Intermittant
Gradually Decays
Direction
3 Dimensional
Unidirectional
rules for anchor preservation are completely different, if in fact they even exist, when implant anchorage is used. The use of implants as anchors has resulted in a new class of anchor systems, and this is being termed “absolute anchorage.” The implications of absolute anchorage are that the functions of an orthodontic appliance become entirely under the control of the operator, as patient compliance is no longer relied on. Furthermore, the predictability of one’s outcome rises dramatically, as movements can be planned and achieved exactly as intended.
instance, a posterior sextant of teeth may be commonly tied together, effectively splinting them, for the purpose of retracting a single tooth (Fig. 4). The active segment thereby has the root surface area of one tooth, whereas the anchor segment is composed of multiple units, and theoretically would overpower it. Further, there are a myriad of auxiliary devices that are commonly used to augment anchorage. Extraoral devices, such as headgears, are well known, as are intraoral auxiliaries such as lip bumpers, transpalatal arches, and Nance appliances, to name but a few. Some of these strategies are limited by their absolute dependence on patient compliance, and for this reason their efficacy is limited.
However, the reader must be cautioned not to misinterpret the means by which implants impart greater effectiveness to an orthodontic appliance. It must be stressed that implants are not used to apply greater force to the teeth. This would be erroneous, because the optimal force levels needed to move teeth are well understood, and are unchanged. Implants allow for greater expediency and predictability not by allowing greater force application to the active teeth, but rather because they themselves can withstand greater force. As a result, they act as perfect anchors and so can be used to move multiples of teeth simultaneously, and that is where the efficiency is realized (Table 1).
Additionally, there are many subtle details that a clinician includes in routine appliance management to aid in anchor preservation. Modifications to arch wire shape, such as tip backs, toe-ins, cinch backs, and stopped arches, are but a few of the commonly used wire bends for enhancing anchorage, all of which become obviated when implant absolute anchorage is used. The means by which an implant integrates into bone offers a very different attachment apparatus than that possessed by a natural tooth.The ligamentous attachment that a tooth features enables it to impart pressure and tension to its surrounding alveolar bone, which in turn responds by resorption and deposition, respectively, allowing a tooth to be moved through bone. An integrated implant, on the other hand, is stabilized in bone by the process of osseointegration, defined as an extremely close proximity of bone to the implant surface, as visualized at the electron microscopy level. As there is no intervening layer of connective tissue, or ligament, by definition an implant is virtually fused to its investing bone. Consequently, it does not impart pressure or tension to its bony housing in the way that a tooth does, and so when forces are placed on it, the implant resists movement, acting much as an ankylosed tooth might. Using an implant as an anchor unit has been well studied and is very reliable, in this author’s experience. The
All implant anchor systems fall into 1 of 2 categories: direct or indirect. There is great flexibility and variety within these offerings, and the rest of this article is dedicated to illustrating these modalities.
Direct Anchorage Direct anchorage is defined as enhanced anchorage using forces that originate from the actual implant. As a source of direct anchorage, either implants or mini-screws can be used, depending on the situation. Implant Driven An implant-driven direct anchorage system would be characterized by an osseointegrated dental implant located in a dental location (that of a tooth) and most commonly already restored, either provisionally or in final form.This implant restoration is then bracketed as a natural tooth would be, by bonding an orthodontic bracket to it and then in turn including this implant-supported tooth in the appliance, and applying force to it either by elastic or coil spring (to pull or push against it, respectively). The implant, once osseointegrated,
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can easily overpower the tooth or teeth that are intended to be mobilized. An implant used in this way is a very reliable source of anchorage. Within physiologic limits, rigid endosseous implants provide excellent orthodontic and orthopedic anchorage.4,6 Indeed, in this author’s studies, in which single implants were used to both protract and retract teeth, the implants were observed to act as perfect anchors. Whereas the teeth involved in direct-anchor studies displayed signs of movement (disappearance of lamina dura, widening of ligament spaces, mobility, and movement) integrated implants invariably did not. Moreover, it has been observed that implants not only withstand orthodontic force, but they seem to adapt to it, strengthening in response to orthodontic load.“Static load applied laterally to implants resulted in a structural adaptation of the peri-implant bone,” according to Gotfredsen et al.5 As a result of these findings, direct-anchor systems can be used quite successfully with seeming disregard for the aforementioned dictates of natural tooth anchor systems. More specifically, it is no longer necessary for the anchor units to outnumber the active units, as a single implant can easily overpower numerous natural teeth and withstand the forces necessary to mobilize the active segment. So much so, that now the active segment can actually outnumber the anchor segment, effectively reversing the rules of anchor preservation from the natural dentition (Fig. 5).
Figure 5. These images represent a direct implant anchor system. In the first clinical slide (A), mesial collapse of the lower left quadrant is evident, as is considerable overlap between the lateral incisor and cuspid. Without posterior teeth as anchor units, retraction of this segment is impossible by conventional orthodontic means. In (B), an implant is placed preparatory to orthodontics, in a somewhat posterior position. After integration, a provisional restoration is placed and the orthodontic appliance secured and activated using the implant as the sole source of anchorage to retract 3 teeth simultaneously. In (C), the result is seen. Contrast the Anchor:Active tooth ratio of this setup to the one depicted in the natural dentition example given in Fig. 4.
A
B
Mini-Screw Driven When an absolute direct-anchor system is mini-screw driven, many of the previously discussed advantages also apply, but there are some distinct differences. Most notably, the miniscrew is not destined to ever function as a tooth replacement, and so its presence is temporary. Consequently, these devices have become widely known as temporary anchorage devices, or TADs. Their relative ease of placement and removal has facilitated their acceptance and popularity, but there are also other features worthy of mention. For one, they offer great flexibility in location. A TAD is often used when extradental anchorage is desirable, and they can be placed in various locations, not dictated by an eventual dental restoration, and so are placed to maximize orthodontic mechanical advantage and force vector optimization. Common locations include interradicular, retromolar, palatal, and even subapically, as might be advantageous for intrusive movements. TADs also feature the ability to apply extradental anchorage in fully dentate cases (Fig. 6).
C
Indirect Anchorage Defined as enhanced anchorage using an implant to stabilize dental units, which in turn serve as the anchor units, indirect anchorage opens absolute anchor possibilities that can be even more flexible and dramatic than direct-anchor setups. Indirect-anchor setups will entail an implant, or TAD, placed
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in a nondental location, which is then used to stabilize teeth, rendering them as indirect absolute anchors, on which orthodontic force is placed. Locations for indirect anchors include retromolar, buccal vestibule, and midpalatal. As they are not
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Figure 6. An example of a direct anchor system to a mini-screw is shown. An orthodontic mini-screw is placed in the buccal just distal to the cuspid tooth and a nickel-titanium coil spring is attached directly to it and the posterior tooth for the purpose of posterior protraction into the extraction space. In this way, the archwire acts merely as a guide, and the mini-screw provides the means of force application.
Figure 8. (A) and (B) illustrate the use of a midpalatal implant as an indirect anchor. By virtue of the connection of the implant to the maxillary molars through the transpalatal bar, those teeth are rendered as indirect absolute anchors and the significant anterior retraction that is shown is easily accomplished.
A
B Figure 7. Presented is a diagram of a Straumann Ortho System (Straumann USA LLC; Andover, MA) midpalatal implant, as well as its solderable abutment and abutment screw. Much of the technology for the implementation of this implant comes from their convention implant design.
largely responsible for the advances in absolute anchorage that have ensued. When the anchor system is no longer needed, the implant is explanted. The next generation of indirect anchors were midpalatal implants (Fig. 7). In these systems, a midpalatal implant is used to establish absolute indirect anchorage by securing to a transpalatal arch to contralateral teeth, thereby rendering those teeth as absolute indirect anchors against which quite dramatic en masse movements can be achieved (Fig. 8). As with all indirect anchors, some time after the implant’s use as an anchor, it is explanted.
destined for restoration or any functional use after serving as anchor units, all indirect-anchor devices are explanted at some time after the completion of orthodontics. Consequently, all indirect-anchor devices, be they endosseous implants or mini-screws, must be considered TADs.
In this author’s experience, the use of midpalatal implants exhibited many features that gave it great versatility. When applied to the adolescent case type (usually achieved by implant locations that are para-median) the complete elimination of the need for headgear and other extraoral auxiliaries was
Implant Driven The retromolar implant was first popularized by Roberts,7 and the success and research associated with that work is
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Figure 9. This is an example of an orthodontic miniscrew, in this case a Dentaurum Tomas (Dentaurum USA; Newton, PA) variant. The cross-hatch design of the slots in the head of the miniscrew allow the insertion of an orthodontic archwire, should the user desire an indirect anchor mechanism. Various auxiliaries such as elastomerics and springs can also be secured to the device.
Figure 10. The use of a Dentaurum Tomas miniscrew as an indirect means of anchorage is illustrated. Observe how an orthodontic archwire is luted to the head of the mini-screw by light-cured resin, thereby engaging it. This same wire then intersects the orthodontic base arch by virtue of a prefabricated T-loop, which enables it to stabilize the wire. An open-coil spring is engaged for the purpose of distalizing the maxillary molars and the premolar is prevented from moving mesially by the anchor system.
within reach, rendering such compliance-dependent devices as completely obsolete. Further development of this technology led to the placement of multiple palatal implants, which would in turn allow the clinician to secure orthopedic appliances, such as palatal expanders, without attaching to teeth. Nevertheless, despite relative ease of management and high success rates, the popularity of midpalatal implants did not achieve widespread acceptance, as was hoped, despite the fact that it allowed treatment possibilities that were otherwise unattainable. This was largely because of market forces, in this author’s opinion, and perhaps also to the rise in popularity of mini-screws, which are somewhat less invasive and further simplified.
Figure 11. (A) and (B) depict the combined use of an orthodontic mini-screw, or TAD for the purpose of securing a Class I elastomeric in conjunction with Invisalign therapy. Full arch retraction can be effected in this way. The aligners are programmed with “precision cuts” on the maxillary cuspids to allow the elastic to be fastened by the patient each time the aligner is placed. In this way, the elastomeric provides the necessary force and the aligners provide the guidance.
Mini-Screw Driven Mini-screws have gained great popularity as indirect anchors as well; however, they must feature one simple design inclusion in the head to allow this application. For a mini-screw to function as an indirect anchor, there must be some means by which an auxiliary can be fastened to it, thereby joining it to the orthodontic appliance. This necessitates that the head of the screw possess some form of a receptacle so designed to accept this attachment (Fig. 9). Usually this is accomplished by machining in the head of the screw a cross-hatch arrangement into which orthodontic wire of a specified size can be inserted, and secured, most commonly by the application of light-cured resin (Fig. 10).
A
B
Consequently, a great feature of mini-screw–assisted anchorage is their great flexibility in location. Mini-screws can be placed in a myriad of locations, as dictated by orthodontic force vectors, and joined to the appliance with ease for maximum efficiency.
Miniscrews in Combination with Aligner Therapy
dramatic shift in acceptability and awareness, largely because of the invention and acceptance of clear aligner therapy. The combination of computer-generated virtual treatment with
Orthodontic care, particularly for adults in the permanent or even late transitional dentition stage, has undergone a
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Figure 12. (A) This case shows a very simple and elegant way to use aligner therapy to achieve unilateral distal driving. A unilateral Class II division 2 case (or a subdivision) is shown and is characterized by a leftside Class II occlusion and corresponding labially locked upper left lateral incisor. (B) Illustration of the force system, which is composed of a palatally placed interadicular TAD and a bonded power arm to the bicuspid. A nickel-titanium coil spring links the two. The power arm permits the application of force well down the root surface, at or even apical to the tooth’s center of rotation. In this way, bodily movements can very efficiently be achieved. (C) A clinical intraoral view illustrating how streamlined this force system is. Also visible in these photos is the aligner, which is programmed to provide the guidance for the movement. (D) After 10 months of therapy, the ideal arch alignment has been achieved. The power arm has been debonded and the mini-screw will subsequently be removed.
sequential appliance manufacture has provided a means by which tooth movement can be planned and executed in a manner that is far more acceptable than conventional fixed or removable appliances. Consequently, there has been a noticeable rise in the administration of orthodontic care and over a broader age range than has previously been the norm; however, with this trend in mind, a few caveats still remain, and will remain, in the opinion of the author.
understanding of orthodontics, particularly diagnosis and treatment planning, remains essential to the successful implementation of this treatment. Orthodontic treatment by its very nature requires a thorough understanding and appreciation for the physiology of tooth movement and treatment goals as well as compromises. In addition, an appreciation of proper retention strategies and retainer design is of great importance, again pointing to the understanding that this is merely another appliance, not a magical change in the way teeth will respond and stabilize. Orthodontic treatment can be fraught with unintended, unanticipated, and untoward side effects, and aligner therapy cannot be relied on to eliminate these deterrents. Operator
Of paramount importance is the understanding that clear aligner therapy represents a removable appliance technique, and although vastly superior to any previous removable appliance, it is still just that; an appliance technique. Consequently, it is the firm assertion of this author that a complete
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experience and expertise remain important and essential ingredients to successful implementation, which computergenerated suggestions cannot and likely will not ever provide a substitute for.
allow this; the auxiliary fasteners can be included in the manufacturing of each set from the outset. Consequently, a wide array of case types of greater sophistication can be accommodated with ease. Further, the use of extradental sources of anchorage, such as mini-screws, can now also be easily accommodated and combined with aligner therapy, opening possibilities to other treatment and outcome possibilities.The reader is directed to the cases presented herein (Figs. 11 and 12) for a graphic representation of such cases.
Aligner therapy realizes other advantages over conventional orthodontic treatment, by either fixed or removable modalities, some of which are logistic in nature. For example, fewer visits, as well as fewer emergency repairs (for debonded brackets or extruding archwires, for example), rank high among them. Less-frequent visits and a longer interval between regular visits is attractive to many patients, 6 to 8 weeks becoming the norm as compared with 4 to 6 weeks. Much less discomfort is reported from patients, as aligners are much less bulky and obtrusive than fixed appliances or conventional removables, especially with regard to the maxillary arch, because palatal coverage is no longer needed. Aligners are certainly more hygienic than fixed appliances by virtue of the fact that they are removed for eating and so are not retentive to food at all, and then afford the ability to brush and floss an unencumbered natural dentition before replacing them in the mouth. For the operator, a great feature of aligner treatment is significantly reduced chair time. This is appreciated because the case is designed and manufactured “up front” and succeeding appointments are for very minor procedures (such as bonding of “attachments” and “interproximal reduction”), but usually for progress check and dispensing of subsequent aligners.There is virtually no adjustment or manipulation of the actual appliances. Last, although the aforementioned advantages are by no means complete, the main advantage to aligner therapy is the very reason patients have flocked to it, in that they are virtually unnoticeable in public or social settings!
Conclusion Implant dentistry is here to stay, certainly in the restorative arenas, but the orthodontic benefits to be gained by planning for, or more importantly, using them as part of mechanotherapy, promises to expand our treatment possibilities and greatly improve efficiency and predictability. The same can be said for aligner therapy in orthodontics; it is here to stay. The benefits to this treatment modality are becoming widely recognized. Moreover, it is this author’s contention that the combination of mini-screws with aligner therapy represents an exciting and viable direction for orthodontic care to develop.
REFERENCES
When Invisalign (Align Technology; San Jose, CA) was first introduced, it was considered by many to be a modality suitable for minimally to moderately involved situations, particularly with regard to crowding or spacing. Many practitioners, perhaps those well aware of their own limitations, continue to use it solely for these situations, such as Class I malocclusions. However, with training and experience, the ability to apply it to more challenging and involved case types becomes the norm. Furthermore, as the art and science developed, there have been significant modifications and improvements to the modality that has further expanded the application. It is now safe to say that clear aligner therapy has gained acceptability far beyond what many had originally anticipated, and that orthodontic offices that now offer clear aligners as their exclusive, if not preferred, appliance design, are becoming more commonplace. A significant advancement is represented by the provision for “precision cuts” and “button cutouts,” enabling providers to include and implement interarch elastics with great ease. No longer is it necessary to modify each aligner by hand to
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Celenza F. Orthodontically induced gingival and alveolar augmentation: clinical and histological findings. Pract Proced Aesthet Dent 2001;13(2):173-5.
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Atherton JD, Kerr NW. Effect of orthodontic tooth movement upon the gingivae. An investigation. Br Dent J 1968;124(12):555-60.
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Atherton ND. The gingival response to orthodontic tooth movement. Am J Orthod 1970;58(2):179-86.
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Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontal 1993;63(12):995-6.
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Roberts WE, Helm FR, Marshall KJ, Gongloff RK. Rigid endosseous implants for orthodontic and orthopedic anchorage. Angle Orthod 1989;59:247-56.
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Roberts WE, Marshall KJ, Mozsary PG. Rigid endosseous implant utilized as anchorage to protract molars and close an atrophic extraction site. Angle Orthod 1990;60:135-52.
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Higuchi KW, Slack JM. The use of titanium fixtures for intraoral anchorage to facilitate orthodontic tooth movement. Int J Oral Maxillofac Implants 1991;6:338-44.
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Odman JK, Lekholm U, Jemt T, Thilander B. Osseointegrated implants as orthodontic anchorage in the treatment of partially edentulous adult patients. Eur J Ortho 1994;16:187-201.
10. Roberts WE, Smith RK, Smilbermann Y. Osseous adaptation to continuous loading of rigid endosseous implants. Am J Orthod 1984;56:95-111. 11. Block MS, Hoffman DR. A new device for absolute anchorage for orthodontics. Am J Orthod 1995;107:251-8.
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Journal of evidence-based dental practice Special Issue—Periodontal and Implant Treatment 12. Wehrbein J, Merz BR, Hammerle CHF, Lang NP. Bone-to-implant contact of orthodontic implants in humans subjected to horizontal loading. Clin Oral Implants Res 1998;9:348-53.
16. Celenza F, Hochman M. Absolute anchorage in orthodontics: direct and indirect implant-assisted modalities. J Clin Orthod 2000;34(7):397-402. 17. Celenza F. Orthodontics: the next implant revolution. Implant Realities 2003;I(3):16-8.
13. Wehrbein H, Merz BR. Aspects of the use of endossseous palatal implants in orthodontic therapy. J Esthet Dent 1998;10:315-24.
18. Celenza F. Implants in orthodontics: the impact of new treatment modalities. US Dent 2006;43-4.
14. Wehrbein H, Merz BR, Hammerle CHF, Lang NP. Bone to implant contact of orthodontic implants in humans subjected to horizontal loading. Clin Oral Implants Res 1998;9:348-53.
19. Smalley W. Implants for tooth movement: determining implant location and orientation. J Esthet Dent 1995;7(2):62-72.
15. Celenza F. Implant enhanced tooth movement: indirect absolute anchorage. Int J Periodontics Restorative Dent 2003;23(6):533-41.
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Implant Interactions with Orthodontics Frank Celenza, DDS
Abstract
Private practice; New York, NY 10021; Private practice, Englewood Cliffs, NJ 07632 Corresponding Author: Frank Celenza, DDS, 880 Fifth Avenue, New York, NY 10021; E-mail: [email protected]. J Evid Base Dent Pract 2012:S1: [192-201] 1532-3382/$36.00 © 2012 Elsevier Inc. All rights reserved.
Many situations arise in which orthodontic therapy in conjunction with implant modalities is beneficial, relevant or necessary. These situations might entail orthodontic treatment preparatory to the placement of an implant, such as in the site preparation for implant placement. Traditionally, this has been somewhat well understood, but there are certain guidelines that must be adhered to as well as diagnostic steps that must be followed. Provision of adequate space for implant placement is of paramount importance, but there is also the consideration of tissue manipulation and remodeling which orthodontic therapy can achieve very predictably and orthodontists should be well versed in harnessing and employing this modality of site preparation. In this way, hopeless teeth that are slated for extraction can still be utilized by orthodontic extraction to augment tissues, both hard and soft, thereby facilitating site development. On the corollary, and representing a significant shift in treatment sequencing, there are many situations in which orthodontic mechanotherapy can be simplified, expedited, and facilitated by the placement of an implant and utilization as an integral part of the mechanotherapy. Implants have proven to provide excellent anchorage, and have resulted in a new class of anchorage known as “absolute anchorage”. Implants can be harnessed as anchors both in a direct and indirect sense, depending upon the dictates of the case. Further, this has led to the development of orthodontic miniscrew systems and techniques, which can have added features such as flexibility in location and placement, as well as ease of use and removal. As orthodontic appliances evolve, the advent of aligner therapy has become mainstream and well accepted, and many of the aforementioned combined treatment modalities can and should be incorporated into this relatively new treatment modality as well.
Introduction
W
hereas the acceptance of implant therapy has deeply affected the surgical and restorative specialties, it has been this author’s observation that the specialty of orthodontics has not experienced this transformation in nearly as dramatic a fashion. Although orthodontists have clearly become aware of implant modalities and incorporated them into treatment plans, for the most part, the dayto-day practice of orthodontics has not changed greatly, certainly not to the extent that the other specialties have had to undergo transformation. For the most part, the orthodontist may be aware that a congenitally missing tooth, for example, will now be replaced by an implant-supported restoration instead of a multiunit bridge,
Keywords: Implant, orthodontics, anchorage, miniscrew, tad, invisalign, interdisciplinary site development
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periodontal ligament as a result of orthodontic stimuli. Additionally, the gingival and soft tissues also respond to tooth movement.
Figure 1. These radiographs depict the situation of 2 seemingly hopeless maxillary central incisors, on the left, and the use of orthodontic site development. The right side is after 4 months of orthodontic eruption and 4 months of stabilization, illustrating the alteration of what would have been a severe extraction socket into an incipient one, making for a much more favorable implant placement environment.
A recent study quantified the benefits of “Orthodontic Extraction” and found the efficacy of regenerating hard tissue to be 70% and that for gingival augmentation to be 60%.1 Further, the residual attachment level of a tooth was not considered to be a limitation. As eruption is a purely vertical movement, and occurs in such a way that the existing attachment around a tooth is placed under pure tension, it does not seem to be insulting to the periodontal attachment apparatus if there is pathology present. More specifically, it seems that when a root is erupted, even if there are cytotoxic regions on that root surface, because it is being moved away from its investing attachment, the periodontal ligament is not insulted and will continue to impart tension to its bony margins and result in deposition. This is often observed despite the presence of an inflammatory environment. What this means is that even in severely compromised teeth, which are destined for extraction, the positive physiologic benefits of orthodontic tissue alteration can still be harnessed to result in morphologic remodeling, or site development. Orthodontic extrusion of teeth with advanced periodontal disease can still have positive clinical and histologic results.2
and so may consequently pay more attention to tooth position and parallelism to facilitate this restoration, but that largely does not change the sequencing, execution, or timing of the treatment, in the orthodontist’s mind. Nonetheless, it is this author’s contention that the specialty of orthodontics is poised, when armed with an understanding of the power and flexibility of implants, to experience a transformation not unlike the aforementioned specialties encountered. When adopted as an integral component of an orthodontic appliance, implants offer the ability to dramatically alter conventional mechanotherapy. The implications range from increased predictability, to simplified mechanics, elimination of patient compliance, decreased treatment time, and perhaps most importantly, expanded treatment possibilities.
As a result of this body of knowledge, teeth that have historically been labeled as hopeless, and slated for extraction, can still be used for physiologic benefit, when appropriate, to impart orthodontic augmentation, or site development. Such teeth, although hopeless, are thereby not to be considered useless, as there is biologic benefit to be realized before their eventual extraction (Fig. 1). Last, and perhaps most importantly, the tissue that is formed by virtue of this orthodontic augmentation, has been shown to be vital tissue3 (Fig. 2). This is because this tissue is formed through the body’s reparative capacity, remodeling in response to orthodontic stimulus, and so it results from physiologic alteration. Unlike allografts and even transplanted tissues of autografts, this tissue is naturally formed in its location. This vital tissue has beneficial implications with respect to subsequent demands placed on it, such as osseointegration to a planned implant placement.
The purpose of this article was to delineate and illustrate some interactions between orthodontics and implants that may be commonly encountered. The topic is divided into 2 distinct phases: the first addressing interactions that orthodontics can effect on sites preparatory to the placement of implants, and the second addressing the effect that implants can have on orthodontics when placed before or during the orthodontic phase and used as part of mechanotherapy.
For Spatial Relations
Orthodontic Interactions Preparatory to Implant Placement
With the advent of implants for tooth replacement, it could be argued that the need for accurate tooth position is more important. Whereas previous tooth replacements might have been accomplished with fixed prostheses, for example, these types of restorations did not require absolute parallelism of roots. In the preparation of a crown or retainer, there is room for correction of less than ideal tooth position, and in the
For Tissue Management Orthodontic tooth movement imparts many alterations on the tissues and supporting structures. It has long been understood that the investing bone tissue remodels in response to pressure and tension that is imparted to it through the
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Figure 2. Here is a histologic image of the bone that was formed through orthodontic stimulus in the previous case. Of particular interest is the appearance of osteocytes within every lacuna, indicating the use of the bodies’ remodeling capacity to form vital bone.
Figure 3. Clinical (A) and radiographic (B) images of a post orthodontic result. Although the incisal edges are properly aligned and the clinical landmarks appear satisfactory for implant placement in the clinical photo, the radiographic picture clearly illustrates inadequate root alignment and space for implant placement.
A
B fabrication of a restoration, new crown contours and “prosthetic tooth positioning” can and routinely do occur. However, if a missing tooth is to be replaced by an implant, the need for accurate site preparation in terms of special relations becomes paramount. Planning for an implant requires a minimum intercoronal space, as was needed in the fixed restoration. More importantly, the implant modality also dictates that there is proper interradicular space to permit the surgical placement of the device and to ensure that root damage to the neighboring teeth is prevented. Consequently, parallelism of teeth, and roots, is essential, and accomplishing this requires that the orthodontic phase of implant site preparation be monitored at the radiographic level, not by clinical visualization. With the use of modern edgewise straightwire appliances, the process of bracket placement on the actual teeth is necessarily an important, if not the most important, step in the set up of a case. With time and experience, most practitioners become adept at direct bonding by sight, usually relying on dental anatomy and landmarks for reference.This method usually suffices for most situations, but the clinician is cautioned to be wary of deviations in crown contour, wear, and root angulations that are frequently encountered in semiedentulous cases. Only by carefully evaluating accurate radiographs will these deviations be appreciated. Further, goodquality periapical radiographs are preferable in this context, owing to their higher level of detail and more reliable orientation than a panorex. In any case, the practitioner is well advised to position bracket placements with consideration to radiographic landmarks, not clinical (Fig. 3).
Orthodontic Interactions After Implant Placement The orthodontist manages equal and opposite actions by controlling anchorage, which is defined as a body’s resistance to displacement. When the anchor units are natural teeth, as they traditionally have been, then they are equally susceptible to movement as are the active teeth. Various measures are taken to ensure that the desirable movements occur and the anchor segments are preserved, but anchor management remains at the very core of orthodontic challenges. Most frequently, in the natural dentition, anchor segments overpower active segments by outnumbering them. For
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Figure 4. A potential anchorage system in the natural dentition. An orthodontic fixed appliance is used as a splint to join all of the teeth from the lateral incisor posteriorly to effectively outnumber the single active central incisor tooth thereby enabling its controlled movement.
TABLE 1. This table compares the function dictates in 3 aspects between an occlusally loaded implant and an orthodontically loaded one. In all 3 regards, orthodontic load is significantly less taxing. Magnitude
Dental Implant
Ortho Implant
High (Kg)
Low (Oz)
Duration
Intermittant
Gradually Decays
Direction
3 Dimensional
Unidirectional
rules for anchor preservation are completely different, if in fact they even exist, when implant anchorage is used. The use of implants as anchors has resulted in a new class of anchor systems, and this is being termed “absolute anchorage.” The implications of absolute anchorage are that the functions of an orthodontic appliance become entirely under the control of the operator, as patient compliance is no longer relied on. Furthermore, the predictability of one’s outcome rises dramatically, as movements can be planned and achieved exactly as intended.
instance, a posterior sextant of teeth may be commonly tied together, effectively splinting them, for the purpose of retracting a single tooth (Fig. 4). The active segment thereby has the root surface area of one tooth, whereas the anchor segment is composed of multiple units, and theoretically would overpower it. Further, there are a myriad of auxiliary devices that are commonly used to augment anchorage. Extraoral devices, such as headgears, are well known, as are intraoral auxiliaries such as lip bumpers, transpalatal arches, and Nance appliances, to name but a few. Some of these strategies are limited by their absolute dependence on patient compliance, and for this reason their efficacy is limited.
However, the reader must be cautioned not to misinterpret the means by which implants impart greater effectiveness to an orthodontic appliance. It must be stressed that implants are not used to apply greater force to the teeth. This would be erroneous, because the optimal force levels needed to move teeth are well understood, and are unchanged. Implants allow for greater expediency and predictability not by allowing greater force application to the active teeth, but rather because they themselves can withstand greater force. As a result, they act as perfect anchors and so can be used to move multiples of teeth simultaneously, and that is where the efficiency is realized (Table 1).
Additionally, there are many subtle details that a clinician includes in routine appliance management to aid in anchor preservation. Modifications to arch wire shape, such as tip backs, toe-ins, cinch backs, and stopped arches, are but a few of the commonly used wire bends for enhancing anchorage, all of which become obviated when implant absolute anchorage is used. The means by which an implant integrates into bone offers a very different attachment apparatus than that possessed by a natural tooth.The ligamentous attachment that a tooth features enables it to impart pressure and tension to its surrounding alveolar bone, which in turn responds by resorption and deposition, respectively, allowing a tooth to be moved through bone. An integrated implant, on the other hand, is stabilized in bone by the process of osseointegration, defined as an extremely close proximity of bone to the implant surface, as visualized at the electron microscopy level. As there is no intervening layer of connective tissue, or ligament, by definition an implant is virtually fused to its investing bone. Consequently, it does not impart pressure or tension to its bony housing in the way that a tooth does, and so when forces are placed on it, the implant resists movement, acting much as an ankylosed tooth might. Using an implant as an anchor unit has been well studied and is very reliable, in this author’s experience. The
All implant anchor systems fall into 1 of 2 categories: direct or indirect. There is great flexibility and variety within these offerings, and the rest of this article is dedicated to illustrating these modalities.
Direct Anchorage Direct anchorage is defined as enhanced anchorage using forces that originate from the actual implant. As a source of direct anchorage, either implants or mini-screws can be used, depending on the situation. Implant Driven An implant-driven direct anchorage system would be characterized by an osseointegrated dental implant located in a dental location (that of a tooth) and most commonly already restored, either provisionally or in final form.This implant restoration is then bracketed as a natural tooth would be, by bonding an orthodontic bracket to it and then in turn including this implant-supported tooth in the appliance, and applying force to it either by elastic or coil spring (to pull or push against it, respectively). The implant, once osseointegrated,
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can easily overpower the tooth or teeth that are intended to be mobilized. An implant used in this way is a very reliable source of anchorage. Within physiologic limits, rigid endosseous implants provide excellent orthodontic and orthopedic anchorage.4,6 Indeed, in this author’s studies, in which single implants were used to both protract and retract teeth, the implants were observed to act as perfect anchors. Whereas the teeth involved in direct-anchor studies displayed signs of movement (disappearance of lamina dura, widening of ligament spaces, mobility, and movement) integrated implants invariably did not. Moreover, it has been observed that implants not only withstand orthodontic force, but they seem to adapt to it, strengthening in response to orthodontic load.“Static load applied laterally to implants resulted in a structural adaptation of the peri-implant bone,” according to Gotfredsen et al.5 As a result of these findings, direct-anchor systems can be used quite successfully with seeming disregard for the aforementioned dictates of natural tooth anchor systems. More specifically, it is no longer necessary for the anchor units to outnumber the active units, as a single implant can easily overpower numerous natural teeth and withstand the forces necessary to mobilize the active segment. So much so, that now the active segment can actually outnumber the anchor segment, effectively reversing the rules of anchor preservation from the natural dentition (Fig. 5).
Figure 5. These images represent a direct implant anchor system. In the first clinical slide (A), mesial collapse of the lower left quadrant is evident, as is considerable overlap between the lateral incisor and cuspid. Without posterior teeth as anchor units, retraction of this segment is impossible by conventional orthodontic means. In (B), an implant is placed preparatory to orthodontics, in a somewhat posterior position. After integration, a provisional restoration is placed and the orthodontic appliance secured and activated using the implant as the sole source of anchorage to retract 3 teeth simultaneously. In (C), the result is seen. Contrast the Anchor:Active tooth ratio of this setup to the one depicted in the natural dentition example given in Fig. 4.
A
B
Mini-Screw Driven When an absolute direct-anchor system is mini-screw driven, many of the previously discussed advantages also apply, but there are some distinct differences. Most notably, the miniscrew is not destined to ever function as a tooth replacement, and so its presence is temporary. Consequently, these devices have become widely known as temporary anchorage devices, or TADs. Their relative ease of placement and removal has facilitated their acceptance and popularity, but there are also other features worthy of mention. For one, they offer great flexibility in location. A TAD is often used when extradental anchorage is desirable, and they can be placed in various locations, not dictated by an eventual dental restoration, and so are placed to maximize orthodontic mechanical advantage and force vector optimization. Common locations include interradicular, retromolar, palatal, and even subapically, as might be advantageous for intrusive movements. TADs also feature the ability to apply extradental anchorage in fully dentate cases (Fig. 6).
C
Indirect Anchorage Defined as enhanced anchorage using an implant to stabilize dental units, which in turn serve as the anchor units, indirect anchorage opens absolute anchor possibilities that can be even more flexible and dramatic than direct-anchor setups. Indirect-anchor setups will entail an implant, or TAD, placed
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in a nondental location, which is then used to stabilize teeth, rendering them as indirect absolute anchors, on which orthodontic force is placed. Locations for indirect anchors include retromolar, buccal vestibule, and midpalatal. As they are not
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Figure 6. An example of a direct anchor system to a mini-screw is shown. An orthodontic mini-screw is placed in the buccal just distal to the cuspid tooth and a nickel-titanium coil spring is attached directly to it and the posterior tooth for the purpose of posterior protraction into the extraction space. In this way, the archwire acts merely as a guide, and the mini-screw provides the means of force application.
Figure 8. (A) and (B) illustrate the use of a midpalatal implant as an indirect anchor. By virtue of the connection of the implant to the maxillary molars through the transpalatal bar, those teeth are rendered as indirect absolute anchors and the significant anterior retraction that is shown is easily accomplished.
A
B Figure 7. Presented is a diagram of a Straumann Ortho System (Straumann USA LLC; Andover, MA) midpalatal implant, as well as its solderable abutment and abutment screw. Much of the technology for the implementation of this implant comes from their convention implant design.
largely responsible for the advances in absolute anchorage that have ensued. When the anchor system is no longer needed, the implant is explanted. The next generation of indirect anchors were midpalatal implants (Fig. 7). In these systems, a midpalatal implant is used to establish absolute indirect anchorage by securing to a transpalatal arch to contralateral teeth, thereby rendering those teeth as absolute indirect anchors against which quite dramatic en masse movements can be achieved (Fig. 8). As with all indirect anchors, some time after the implant’s use as an anchor, it is explanted.
destined for restoration or any functional use after serving as anchor units, all indirect-anchor devices are explanted at some time after the completion of orthodontics. Consequently, all indirect-anchor devices, be they endosseous implants or mini-screws, must be considered TADs.
In this author’s experience, the use of midpalatal implants exhibited many features that gave it great versatility. When applied to the adolescent case type (usually achieved by implant locations that are para-median) the complete elimination of the need for headgear and other extraoral auxiliaries was
Implant Driven The retromolar implant was first popularized by Roberts,7 and the success and research associated with that work is
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Figure 9. This is an example of an orthodontic miniscrew, in this case a Dentaurum Tomas (Dentaurum USA; Newton, PA) variant. The cross-hatch design of the slots in the head of the miniscrew allow the insertion of an orthodontic archwire, should the user desire an indirect anchor mechanism. Various auxiliaries such as elastomerics and springs can also be secured to the device.
Figure 10. The use of a Dentaurum Tomas miniscrew as an indirect means of anchorage is illustrated. Observe how an orthodontic archwire is luted to the head of the mini-screw by light-cured resin, thereby engaging it. This same wire then intersects the orthodontic base arch by virtue of a prefabricated T-loop, which enables it to stabilize the wire. An open-coil spring is engaged for the purpose of distalizing the maxillary molars and the premolar is prevented from moving mesially by the anchor system.
within reach, rendering such compliance-dependent devices as completely obsolete. Further development of this technology led to the placement of multiple palatal implants, which would in turn allow the clinician to secure orthopedic appliances, such as palatal expanders, without attaching to teeth. Nevertheless, despite relative ease of management and high success rates, the popularity of midpalatal implants did not achieve widespread acceptance, as was hoped, despite the fact that it allowed treatment possibilities that were otherwise unattainable. This was largely because of market forces, in this author’s opinion, and perhaps also to the rise in popularity of mini-screws, which are somewhat less invasive and further simplified.
Figure 11. (A) and (B) depict the combined use of an orthodontic mini-screw, or TAD for the purpose of securing a Class I elastomeric in conjunction with Invisalign therapy. Full arch retraction can be effected in this way. The aligners are programmed with “precision cuts” on the maxillary cuspids to allow the elastic to be fastened by the patient each time the aligner is placed. In this way, the elastomeric provides the necessary force and the aligners provide the guidance.
Mini-Screw Driven Mini-screws have gained great popularity as indirect anchors as well; however, they must feature one simple design inclusion in the head to allow this application. For a mini-screw to function as an indirect anchor, there must be some means by which an auxiliary can be fastened to it, thereby joining it to the orthodontic appliance. This necessitates that the head of the screw possess some form of a receptacle so designed to accept this attachment (Fig. 9). Usually this is accomplished by machining in the head of the screw a cross-hatch arrangement into which orthodontic wire of a specified size can be inserted, and secured, most commonly by the application of light-cured resin (Fig. 10).
A
B
Consequently, a great feature of mini-screw–assisted anchorage is their great flexibility in location. Mini-screws can be placed in a myriad of locations, as dictated by orthodontic force vectors, and joined to the appliance with ease for maximum efficiency.
Miniscrews in Combination with Aligner Therapy
dramatic shift in acceptability and awareness, largely because of the invention and acceptance of clear aligner therapy. The combination of computer-generated virtual treatment with
Orthodontic care, particularly for adults in the permanent or even late transitional dentition stage, has undergone a
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Figure 12. (A) This case shows a very simple and elegant way to use aligner therapy to achieve unilateral distal driving. A unilateral Class II division 2 case (or a subdivision) is shown and is characterized by a leftside Class II occlusion and corresponding labially locked upper left lateral incisor. (B) Illustration of the force system, which is composed of a palatally placed interadicular TAD and a bonded power arm to the bicuspid. A nickel-titanium coil spring links the two. The power arm permits the application of force well down the root surface, at or even apical to the tooth’s center of rotation. In this way, bodily movements can very efficiently be achieved. (C) A clinical intraoral view illustrating how streamlined this force system is. Also visible in these photos is the aligner, which is programmed to provide the guidance for the movement. (D) After 10 months of therapy, the ideal arch alignment has been achieved. The power arm has been debonded and the mini-screw will subsequently be removed.
sequential appliance manufacture has provided a means by which tooth movement can be planned and executed in a manner that is far more acceptable than conventional fixed or removable appliances. Consequently, there has been a noticeable rise in the administration of orthodontic care and over a broader age range than has previously been the norm; however, with this trend in mind, a few caveats still remain, and will remain, in the opinion of the author.
understanding of orthodontics, particularly diagnosis and treatment planning, remains essential to the successful implementation of this treatment. Orthodontic treatment by its very nature requires a thorough understanding and appreciation for the physiology of tooth movement and treatment goals as well as compromises. In addition, an appreciation of proper retention strategies and retainer design is of great importance, again pointing to the understanding that this is merely another appliance, not a magical change in the way teeth will respond and stabilize. Orthodontic treatment can be fraught with unintended, unanticipated, and untoward side effects, and aligner therapy cannot be relied on to eliminate these deterrents. Operator
Of paramount importance is the understanding that clear aligner therapy represents a removable appliance technique, and although vastly superior to any previous removable appliance, it is still just that; an appliance technique. Consequently, it is the firm assertion of this author that a complete
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experience and expertise remain important and essential ingredients to successful implementation, which computergenerated suggestions cannot and likely will not ever provide a substitute for.
allow this; the auxiliary fasteners can be included in the manufacturing of each set from the outset. Consequently, a wide array of case types of greater sophistication can be accommodated with ease. Further, the use of extradental sources of anchorage, such as mini-screws, can now also be easily accommodated and combined with aligner therapy, opening possibilities to other treatment and outcome possibilities.The reader is directed to the cases presented herein (Figs. 11 and 12) for a graphic representation of such cases.
Aligner therapy realizes other advantages over conventional orthodontic treatment, by either fixed or removable modalities, some of which are logistic in nature. For example, fewer visits, as well as fewer emergency repairs (for debonded brackets or extruding archwires, for example), rank high among them. Less-frequent visits and a longer interval between regular visits is attractive to many patients, 6 to 8 weeks becoming the norm as compared with 4 to 6 weeks. Much less discomfort is reported from patients, as aligners are much less bulky and obtrusive than fixed appliances or conventional removables, especially with regard to the maxillary arch, because palatal coverage is no longer needed. Aligners are certainly more hygienic than fixed appliances by virtue of the fact that they are removed for eating and so are not retentive to food at all, and then afford the ability to brush and floss an unencumbered natural dentition before replacing them in the mouth. For the operator, a great feature of aligner treatment is significantly reduced chair time. This is appreciated because the case is designed and manufactured “up front” and succeeding appointments are for very minor procedures (such as bonding of “attachments” and “interproximal reduction”), but usually for progress check and dispensing of subsequent aligners.There is virtually no adjustment or manipulation of the actual appliances. Last, although the aforementioned advantages are by no means complete, the main advantage to aligner therapy is the very reason patients have flocked to it, in that they are virtually unnoticeable in public or social settings!
Conclusion Implant dentistry is here to stay, certainly in the restorative arenas, but the orthodontic benefits to be gained by planning for, or more importantly, using them as part of mechanotherapy, promises to expand our treatment possibilities and greatly improve efficiency and predictability. The same can be said for aligner therapy in orthodontics; it is here to stay. The benefits to this treatment modality are becoming widely recognized. Moreover, it is this author’s contention that the combination of mini-screws with aligner therapy represents an exciting and viable direction for orthodontic care to develop.
REFERENCES
When Invisalign (Align Technology; San Jose, CA) was first introduced, it was considered by many to be a modality suitable for minimally to moderately involved situations, particularly with regard to crowding or spacing. Many practitioners, perhaps those well aware of their own limitations, continue to use it solely for these situations, such as Class I malocclusions. However, with training and experience, the ability to apply it to more challenging and involved case types becomes the norm. Furthermore, as the art and science developed, there have been significant modifications and improvements to the modality that has further expanded the application. It is now safe to say that clear aligner therapy has gained acceptability far beyond what many had originally anticipated, and that orthodontic offices that now offer clear aligners as their exclusive, if not preferred, appliance design, are becoming more commonplace. A significant advancement is represented by the provision for “precision cuts” and “button cutouts,” enabling providers to include and implement interarch elastics with great ease. No longer is it necessary to modify each aligner by hand to
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